Method for communicating in mobile system

ABSTRACT

The present invention relates to a method for communicating from a primary station to a plurality of secondary station, comprising the step of at the primary station allocating a resource to the secondary stations over the time on the basis of a hash function, wherein the hash function is such that the probability that two secondary stations are allocated common resources in two subframes substantially equals the product of the probability that the two secondary stations are allocated a common resource in the first subframe and the probability that the two secondary stations are allocated a common resource in the second subframe.

FIELD OF THE INVENTION

The present invention relates to a method for communicating between aprimary station and a plurality of secondary stations.

This invention is, for example, relevant for telecommunication systemslike a mobile telecommunication system. More specifically, thisinvention is relevant for the UMTS.

BACKGROUND OF THE INVENTION

In a conventional UMTS system, a PDCCH (Physical Downlink ControlChannel) message can use 1, 2, 4 or 8 Channel Control Elements (CCEs orresource elements)—referred to as CCE aggregation levels 1, 2, 4 or 8. Asearch space is a set of aggregated CCEs (with a certain aggregationlevel) within which a mobile station (or user equipment (UE) orsecondary station) performs blind decoding of all PDCCH payloadspossible for that aggregation level. Search spaces are defined peraggregation level; a secondary station in such a system thus can have upto four search spaces. For example, the search space of a UE foraggregation level 1 (referred to as 1-CCE) could consist of the CCEsindexed 3, 4, 5, 6, 7, 8, while its search space for aggregation level 8could consist of the two resource sets of aggregated CCEs consisting ofthe CCEs indexed by 1, 2, . . . , 8 and 9, 10, . . . , 16, respectively.in this example, the UE thus performs six blind decodings for 1-CCEs andtwo blind decodings for 8-CCEs.

In an example, in order to determine the starting point of the searchspace, mobile stations (or secondary stations, also termed as UEs, forUser Equipments in 3GPP parlance) compute a hash function f(UE_ID,s),where UE_ID is the identifier of the UE (different for distinct UEs) ands a time-varying subframe number. It is desirable that different UEscollide (have equal hash value) as infrequently as possible.

The hash function presently proposed within 3GPP is of the formf(UE_ID,s)=K(UE_ID*16+s)+L modulo M,

where K, L and M are constants, UE ID is the identifier of the UE, and sis the subframe number. It is clear that with this particular hashfunction f, two UEs that collide for some subframe number collidepersistently, i.e., for all subframe numbers.

SUMMARY OF THE INVENTION

It is an object of the invention to propose a method for communicatingwhich permits the probability of collisions to be reduced.

Another object of the invention is to provide a method for communicatingpreventing two UEs from repeatedly colliding.

To this end, according to a first aspect of the invention, a method isproposed for communicating from a primary station to a plurality ofsecondary stations, comprising the step of at the primary stationallocating a resource to the secondary stations over time on the basisof a hash function, wherein the hash function is such that theprobability that two secondary stations are allocated common resourcesin two subframes substantially equals the product of the probabilitythat the two secondary stations are allocated a common resource in thefirst subframe and the probability that the two secondary stations areallocated a common resource in the second subframe.

As a consequence, the hash functions proposed here aim to reduce thelikelihood of persistent collisions. In fact, the hash functions aresuch that the probability that different UEs collide in two subframes isapproximately equal to the probability that two UEs collide in the firstof these subframes times the probability that two UEs collide in thesecond of these subframes. Thus, it is unlikely that two UEs colliderepeatedly.

In a specific embodiment of the method, the hash function has the form:

f(x,s)=(h(x)mod g(s))mod M, where x is a parameter of each secondarystation, s is the subframe number, h is a function dependent on x, g isa function dependent on s, M is a constant, and mod is the modulofunction. In another specific embodiment of the method, h is a constantmultiplier.

The present invention also relates to a secondary station comprisingmeans for communicating with a primary, the secondary station furthercomprising

control means configured to search at least one of a plurality of searchspaces, each search space comprising at least one resource set, where atleast one resource set might be used to transmit a message to theconsidered secondary station, wherein the search space of the secondarystation is determined on the basis of a hash function, wherein the hashfunction is such that the probability that two secondary stations areconfigured to have common resources in the search spaces in both of anytwo subframes substantially equals the product of the probability thatthe two secondary stations are configured to have a common resource inthe first subframe and the probability that the two secondary stationsare configured to have a common resource in the second subframe;

wherein the control means are configured for searching in the configuredat least one search space for a control message from the primary stationaddressed to the considered secondary station, and receiving the controlmessage.

In accordance with still another aspect of the invention, it is proposeda primary station comprising means for communicating with a plurality ofsecondary stations, the primary station further comprising

allocating means to allocate at least one resource set to a givensecondary station into at least one of a plurality of search spaces,each search space comprising at least one resource set, wherein thesearch space of the given secondary station is determined on the basisof a hash function, wherein the hash function is such that theprobability that two secondary stations are configured to have commonresources in the search spaces in both of any two subframessubstantially equals the product of the probability that the twosecondary stations are configured to have a common resource in the firstsubframe and the probability that the two secondary stations areconfigured to have a common resource in the second subframe.

These and other aspects of the invention will be apparent from and willbe elucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described in more detail, by way ofexample, with reference to the accompanying drawings, wherein:

FIG. 1 is a block diagram of a system in accordance with the inventioncomprising a primary station and at least a secondary station.

FIG. 2 is a time chart representing the allocated search spaces inaccordance an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a method for communicating in anetwork, like a cellular network. For instance, the network may be aUMTS network as depicted on FIG. 1.

Referring to FIG. 1, a radio communication system in accordance with theinvention comprises a primary station (BS) 100 and a plurality ofsecondary stations (MS) 110. The primary station 100 comprises amicrocontroller (μC) 102, transceiver means (Tx/Rx) 104 connected toantenna means 106, power control means (PC) 107 for altering thetransmitted power level, and connection means 108 for connection to thePSTN or other suitable network. Each MS 110 comprises a microcontroller(μC) 112, transceiver means (Tx/Rx) 114 connected to antenna means 116,and power control means (PC) 118 for altering the transmitted powerlevel. Communication from primary station 100 to mobile station 110takes place on a downlink channel, while communication from secondarystation 110 to primary station 100 takes place on an uplink channel.

One of the downlink control channels received by the secondary stationsis the PDDCH, where each secondary station has to blindly decode aplurality of sets of CCEs to find which set was allocated to it as setout in the preamble of the description.

In accordance with a first embodiment of the invention, results ofvarious simulations carried out by the inventors are described. Withthese simulations, it is assumed that 48 CCEs are available. Thiscorresponds to the illustrative exemplary first embodiment of theinvention. Various sets of 48 search spaces for the 1-CCEs have beenconsidered; to each user to which a 1-CCE is to be sent, one of these 48search spaces is assigned at random (the choice corresponds to theoutcome of a hash function of that UE that we model as being uniformover the numbers 1, 2, . . . , 48). Each search space consists of sixCCEs in this example. The following sets of search spaces have beenconsidered:

-   S_1: all search spaces contiguous—i.e. of the form {i, i+1, i+2,    i+3, i+4, i+5} with 0≦i≦47 where i is the CCE index, and all    elements modulo 48.-   S_5: all search spaces of the form {i, i+5, i+10, i+15, i+20, i+25}    with 0≦i≦47, and all elements modulo 48.-   S_7: all search spaces of the form {i, i+7, i+14, i+21, i+28, i+35}    with 0≦i≦47, and all elements modulo 48.-   S_d: all search spaces of the form {i, i+1, i+3, i+7, i+12, i+22}    with 0≦i≦47, and all elements modulo 48. S_d is designed so that all    search spaces overlap in just 1 CCE.    So, for example, the search space of S_5 corresponding to i=25    consists of the CCEs indexed by 25, 30, 35, 40, 45, 2 (as 50 modulo    48 equals 2).

FIG. 2 illustrates the use of a pattern enabling the number of resourceelements in common to be minimized in accordance with the firstembodiment, compared with the prior art. On FIG. 2, a set of availableresources 200 are depicted.

In a conventional system, if only sets of 1-CCEs and 8-CCEs areconsidered, the search space for one secondary station or UE for 8-CCEmessages (2 positions 208 are constructed from contiguous groups ofCCEs) is depicted on FIG. 2. The positions 201 of 1-CCE messages (6contiguous positions) are such that it is likely that all possiblepositions are blocked if another UE is receiving an 8-CCE message.

In accordance with the first embodiment of the invention, the set ofavailable resources 300 comprises search space for one LIE for 8-CCEmessages 308, as on FIG. 2 where 2 positions are constructed fromcontiguous groups of CCEs. Regarding the search space for a UE for 1-CCEmessages, 6 non-contiguous positions 301 are represented. Thesepositions are non contiguous, so that they reduce overlap with higheraggregation-level search space and therefore increase likelihood that aposition can be found to send a small message.

In order to determine the start of the search space of each secondarystation, each secondary station uses a hash function. The hash functionsdisclosed in accordance with this embodiment aim to reduce thelikelihood of persistent collisions. In fact, the hash functions aresuch that the probability that different UEs collide in two subframes isapproximately equal to the probability that two UEs collide in the firstof this subframes times the probability that two UEs collide in thesecond of these subframes. Stated differently, collision events indifferent subframes are approximately independent.

In fact, we describe functions f_(s)(x) with x∈X, s∈{0, 1, . . . , T−1}into {0, 1, . . . , M−1}. The variable x corresponds to the UE_ID in thepresent situation, and s to the subframe number. The functions have thefollowing properties.

1. For each s∈{0, 1, . . . , T−1}, the function f_(s) attains eachelement in {0, 1, . . . , M−1} approximately equally often.

2. For all distinct s,t in {0, 1, . . . , T−1}, the number of elements xin X such that f_(s)(x)=i and f_(t)(x)=j is approximately the same forall values of i and j.

We propose to use sets of hash functions of the formf _(s)(x)=(Ax mod M _(s))mod M

where A is a constant number and M₀, M₁, . . . , M_(T-1) are differentnumbers. It is advantageous if M₀, M₁, . . . , M_(T-1) are relativelyprime to each other and to M.

As a variant of the first embodiment, the following parameters areselected:

T=10, UE ID in X={0, 1, . . . , 2²⁴−1}, M=47, and A=1. For themultipliers M₀, M₁, . . . , M₉, we take ten prime numbers close to 2¹²,as depicted in the following table.

To test the “uniformity” of each of the T=10 hash functions, i.e.,Property 1 above we counted for i=0, . . . , M−1, the number of elementsx∈X for which f_(t)(x)=i. The quotient of the smallest of these numbersand the largest of these numbers are computed. In case of a uniformdistribution, this quotient would equal one; we thus wish that thequotient should be approximately one. For our specific choice of M₀, M₁,. . . , M₉, the computed quotients range from 09885 to 09906,

TABLE 1 List of multipliers s M_(s) 0 4057 1 4073 2 4079 3 4091 4 4093 54099 6 5003 7 5009 8 5011 9 5021

To test the independence of the hash functions f_(s) and f_(t), i.e.Property 2 above, we computed for all pairs (i,j) the number elementsx∈X for which f_(s)(x)=i and f_(t)(x)=j,

Next, we computed the quotient of the smallest of these M² number andthe largest of these M² numbers. Ideally, we would like this quotient tobe equal to one. For our specific choice of M₀, M₁, . . . , M₉, thecomputed quotients range from 0.9752 to 0.9808.

We can conclude that in the embodiment, the hash functions areapproximately uniform and approximately independent.

In the envisioned application, the values of T and the range X is fixedwhile M may vary. For implementation reasons, it is advantageous thatM₀, M₁, . . . , M_(T−-1) do not depend on M. If we change M to 24, thecomputed quotients for uniformity range from 0.9941 to 0.9952; thecomputed quotients for testing independence range from 0.9779 to 0.9889.So also for this case, the proposed hash functions are approximatelyuniform and approximately independent. If we change M to 120, thecomputed quotients for uniformity range from 0.9706 to 0.9762; those fortesting independence range from 0.9330 to 0.9474.

The invention may be applicable to mobile telecommunication systems likeUMTS LTE and UMTS LTE-Advanced, but also in some variants to anycommunication system having allocation of resources to be donedynamically or at least semi persistently.

In the present specification and claims the word “a” or “an” precedingan element does not exclude the presence of a plurality of suchelements. Further, the word “comprising” does not exclude the presenceof other elements or steps than those listed.

The inclusion of reference signs in parentheses in the claims isintended to aid understanding and is not intended to be limiting.

From reading the present disclosure, other modifications will beapparent to persons skilled in the art. Such modifications may involveother features which are already known in the art of radiocommunication.

The invention claimed is:
 1. A method for operating a secondary stationfor communicating in a network with a primary station, the methodcomprising: determining at least one search space of a plurality ofsearch spaces of the secondary station, each search space comprising atleast one set of resource elements; controlling an antenna andtransceiver to communicate in the network to receive messages;searching, in a message of the received messages in the at least onedetermined search space for a control message from the primary stationthat is addressed to the secondary station, wherein determining the atleast one search space is based on a hash function f_(s)(x), whereinx∈X, s∈{0, 1, . . . , T−1} into {0, 1, . . . , M−1},wherein xcorresponds to a respective parameter of the secondary stations, scorresponds to a parameter of a subframe, X is a set of the respective xparameters of the secondary stations, T indicates a number of hashfunctions, and M is constant; and wherein the hash function has thefollowing properties: for each s∈{0,1, . . . , T−1}, the function f_(s)attains each element in {0, 1, . . . , M−1}, approximately equallyoften; and for all distinct s,t in {0, 1, . . . , T−1},where t is adifferent subframe number than s, the number of elements x in X is suchthat f_(s)(x)=i and f_(t)(x)=j is approximately the same for all valuesof i and j.
 2. The method of claim 1, wherein the hash function f_(s)(x)results in a substantially uniform probability of configuring each ofthe available resources to a given secondary station in a givensubframe.
 3. The method of claim 1, wherein for two distinct subframess, t, the outputs of the hash functions f_(s)(x), f_(t)(x) aresubstantially independent from each other.
 4. The method of claim 1,wherein the parameter of the secondary station is an identifier of thesecondary station, the identifier being different for each differentrespective secondary station of the network.
 5. The method of claim 1,wherein the hash function has the form:f(x,s)=(h(x)modg(s))modM, where h is a function dependent on x, g is afunction dependent on s, M is a constant, and mod is the modulofunction.
 6. The method of claim 5, wherein h(x) is a constantmultiplier.
 7. The method of claim 5, wherein for each value of s, g(s)is a prime number.
 8. A primary station configured to communicate in anetwork, the primary station comprising: a transceiver and antennaconfigured to enable the primary station to communicate in the networkwith a secondary station; and a control circuit configured to determineat least one search space of a plurality of search spaces of thesecondary station, allocate at least one respective resource set to thesecondary station into the at least one determined search space of theplurality of search spaces of the secondary station, each search spacecomprising at least one set of resource elements; and control thetransceiver and antenna to transmit, on a downlink channel, a controlmessage addressed to the secondary station from the primary stationusing at least a portion of the set of resource elements allocated tothe secondary station; and wherein the at least one determined searchspace of the secondary station is determined by the control circuitbased on a hash function f_(s)(x); wherein x∈X, s∈{0,1, . . . , T−1}into {0, 1, . . . , M−1},wherein x corresponds to a respective parameterof the secondary stations, s corresponds to a parameter of a subframe, Xis a set of the respective x parameters of the secondary stations, Tindicates a number of hash functions, and M is constant, and wherein thehash function has the following properties: for each s∈{0,1, . . . ,T−1}, the function f_(s), attains each element in {0, 1, . . . , M−1},approximately equally often; and for all distinct s,t in {0, 1, . . . ,T−1}, where t is a different subframe number than s, the number ofelements x in X is such that f_(s)(x)=i and f_(t)(x)=j is approximatelythe same for all values of i and j.
 9. A secondary station configured tocommunicate in a network, the secondary station comprising: an antennaand transceiver configured to enable the secondary station tocommunicate in the network; and a control circuit configured to:determine at least one search space of a plurality of search spaces ofthe secondary station, the respective search spaces comprising at leastone set of resource elements; control the antenna and transceiver toreceive messages from the network; search in a message of the receivedmessages in the at least one determined search space to find a controlmessage from a primary station, addressed to the secondary station; andwherein the at least one search space of the secondary station isdetermined based on a hash function f_(s)(x); wherein x∈X, s∈{0,1, . . ., T−1} into {0, 1, . . . , T−1}, wherein x corresponds to a respectiveparameter of the secondary stations, s corresponds to a parameter of asubframe, X is a set of the respective x parameters of the secondarystations, T indicates a number of hash functions, and M is constant, andwherein the hash function has the following properties: for each s∈{0,1,. . . , T−1}, the function f_(s) attains each element in {0, 1, . . . ,M−1}, approximately equally often; and for all distinct s, t in {0, 1, .. . , T−1}, where t is a different subframe number than s, the number ofelements x in X is such that f_(s) (x)=i and f_(t)(x)=j is approximatelythe same for all values of i and j.
 10. The method of claim 1,comprising: allocating, via a control circuit at the primary station, atleast one respective resource set into the at least one determinedsearch space; and controlling a transceiver of the primary station totransmit a control message addressed to the secondary station using theresource set allocated to the secondary station.
 11. The method of claim1, wherein the hash function is such that, when there are pluralsecondary stations, the probability that any two secondary stations areconfigured to have common resources in the search spaces in both a firstsubframe and a second subframe substantially equals the product of theprobability that the two secondary stations are configured to have acommon resource in the first subframe and the probability that the twosecondary stations are configured to have a common resource in thesecond subframe.
 12. The primary station of claim 8, wherein the hashfunction is such that, when there are plural secondary stations, theprobability that any two secondary stations are configured to havecommon resources in the search spaces in both a first subframe and asecond subframe substantially equals the product of the probability thatboth of the two secondary stations are configured to have a commonresource in the first subframe and the probability that the twosecondary stations are configured to have a common resource in thesecond subframe.
 13. The secondary station of claim 9, wherein the hashfunction is such that, when there are plural secondary stations, theprobability that any two secondary stations are configured to havecommon resources in the search spaces in both a first subframe and asecond subframe substantially equals the product of the probability thatboth of the two secondary stations are configured to have a commonresource in the first subframe and the probability that the twosecondary stations are configured to have a common resource in thesecond subframe.
 14. A primary station configured to communicate in anetwork the primary station comprising: a transceiver and antennaconfigured to enable communication by the primary station in the networkwith a secondary station; and a control circuit configured to: determineat least one search space of a plurality of search spaces of thesecondary station; allocate at least one respective resource set to thesecondary station into the at least one determined search space of theplurality of search spaces of the secondary station, the respectivesearch spaces comprising at least one set of resource elements; andcontrol the transceiver and antenna to transmit on a downlink channel, acontrol message addressed to the secondary station, using at least aportion of the resource set allocated to the secondary station; whereinthe at least one search space of the secondary station is determinedbased on a hash function f_(s)(x); wherein the hash function is suchthat, when there are plural secondary stations, the probability that anytwo secondary stations are configured to have common resources in thesearch spaces in both a first subframe and a second subframesubstantially equals the product of the probability that both of the twosecondary stations are configured to have a common resource in the firstsubframe and the probability that the two secondary stations areconfigured to have a common resource in the second subframe.
 15. Asecondary station configured to communicate in a network, the secondarystation comprising: a transceiver and antenna configured to enable thesecondary station to communicate in the network, ; and a control circuitconfigured to: determine at least one search space of a plurality ofsearch spaces of the secondary station, the respective search spacescomprising at least one set of resource elements; control the antennaand transceiver to receive messages from the network; and search in theat least one determined search space in a received message of thereceived messages to find a control message from the primary station,addressed to the secondary station; and wherein the at least one searchspace of the secondary station is determined based on a hash functionf_(s) (x), wherein the hash function is such that, when there are pluralsecondary stations, the probability that any two secondary stations areconfigured to have common resources in the search spaces in both a firstsubframe and a second subframe substantially equals the product of theprobability that both of the two secondary stations are configured tohave a common resource in the first subframe and the probability thatthe two secondary stations are configured to have a common resource inthe second subframe.
 16. A method of operating a primary station forcommunicating in a network, the method comprising: allocating, by acontrol circuit, at least one resource set to at least one of aplurality of search spaces of the secondary station, each search spacecomprising at least one set of resource elements; and controlling, bythe control circuit, a transceiver and antenna to transmit a controlmessage to the secondary station, addressed to the secondary station,using at least a portion of the allocated set of resource elements; andwherein the search space of the secondary station is determined based ona hash function fs(x); and wherein the hash function is such that, whenthere are plural secondary stations, the probability that both of anytwo secondary stations are configured to have common resources in thesearch spaces in both a first subframe and a second subframesubstantially equals the product of the probability that the twosecondary stations are configured to have a common resource in the firstsubframe and the probability that the two secondary stations areconfigured to have a common resource in the second subframe.
 17. Amethod of operating a secondary station for communicating in a network,the method comprising controlling, by a control circuit, a transceiverand antenna to receive messages from the network; and searching, by thecontrol circuit, in at least one search space of the secondary stationin a message of the received messages, to find a control message fromthe primary station, addressed to the secondary station, respectivesearch spaces comprising at least one resource set, where at least oneresource set is for receiving a message from the primary stationaddressed to the secondary station; and wherein the search space of thesecondary station is determined based on a hash function f_(s)(x); andwherein the hash function is such that the probability that twosecondary stations are configured to have common resources in the searchspaces in both a first subframe and a second subframe substantiallyequals the product of the probability that the two secondary stationsare configured to have a common resource in the first subframe and theprobability that the two secondary stations are configured to have acommon resource in the second subframe.
 18. A method of operating aprimary station for communication in a network, the method comprising:determining, by a control circuit, at least one search space of aplurality of search spaces of a secondary station; allocating, by thecontrol circuit, at least one resource set to the secondary station intothe determined at least one search space of the secondary station, eachsearch space comprising at least one set of resource elements; andcontrolling a transceiver and antenna to transmit on a downlink channela control message to the secondary station, addressed to the secondarystation, using at least a portion of the resource set allocated to thesecondary station; and wherein the search space of the secondary stationis determined based on a hash function f_(s),(x); wherein x∈X, s∈{0, 1,. . . , T−1} into {0, 1, . . . , M−1}, wherein x corresponds to arespective parameter of the secondary stations, s corresponds to aparameter of a subframe, X is a set of the respective x parameters ofthe secondary stations, T indicates a number of hash functions, and M isconstant, and wherein the hash function has the following properties:for each s∈{0, 1, . . . , T−1}, the function f_(s), attains each elementin {0, 1, . . . , M−1}, approximately equally often; and for alldistinct s,t in {0, 1, . . . , T−1},where t is a different subframe thans, the number of elements x in X is such that f_(s),(x)=i and f_(t)(x)=jis approximately the same for all values of i and j.
 19. A method ofoperating a secondary station for communication in a network, the methodcomprising: determining, by a control circuit, at least one search spaceof a plurality of search spaces of the secondary station, each searchspace comprising at least one set of resource elements; controlling atransceiver and antenna to communicate in the network to receivemessages; and searching, by the control circuit, in the determined atleast one search space in a message of the received messages, to find acontrol message from a primary station addressed to the secondarystation; and wherein the search space of the secondary station isdetermined based on a hash function f_(s)(x); wherein x∈X, s∈{0, 1, . .. , T−1} into {0, 1, . . . , M−1}, wherein x corresponds to a respectiveparameter of the secondary stations, s corresponds to a parameter of asubframe, X is a set of the respective x parameters of the secondarystations, T indicates a number of hash functions, and M is constant, andwherein the hash function has the following properties: for each s∈{0,1, . . . , T−1},the function f_(s) attains each element in {0, 1, . . ., M−1}, approximately equally often; and for all distinct s,t in {0, 1,. . . , T−1}, where t is a different subframe than s, the number ofelements x in X is such that f_(s)(x)=i and f_(t)(x)=j are approximatelythe same for all values of i and j.
 20. A non-transitorycomputer-readable storage-medium having stored thereon instructions thatwhen executed are configured to cause processing circuitry to: allocateat least one respective resource set to a secondary station into the atleast one determined search space of the plurality of search spaces ofthe secondary station, the respective search spaces comprising at leastone set of resource elements; and control a transceiver and antenna totransmit a control message to the secondary station, addressed to thesecondary station, using at least a portion of the resource setallocated to the secondary station; wherein the search space of thesecondary station is determined based on a hash function f_(s)(x);wherein x∈X, s∈{0, 1, . . . , T−1} into {0, 1, . . . , M−1}, wherein xcorresponds to a respective parameter of the secondary stations, scorresponds to a parameter of a subframe, X is a set of the respective xparameters of the secondary stations, T indicates a number of hashfunctions, and M is constant, and wherein the hash function has thefollowing properties: for each s∈{0, 1, . . . , T−1}, the function f_(s)attains each element in {0, 1, . . . , M−1}, approximately equallyoften; and for all distinct s,t in {0, 1, . . . , T−1}, where t is adifferent subframe than s, the number of elements x in X is such thatf_(s)(x)=i and f_(t)(x)=j is approximately the same for all values of iand j.
 21. A non-transitory computer-readable storage-medium havingstored thereon instructions that when executed cause processingcircuitry to determine at least one search space of a plurality ofsearch spaces of the secondary station, each search space of thesecondary station comprising at least one set of resource elements,control an antenna and transceiver to communicate in the network toreceive messages; search in the determined at least one search space, ina message of the received messages, for a control message from theprimary station, addressed to the secondary station; and wherein thesearch space of the secondary station is determined based on a hashfunction f_(s) (x) wherein x∈X, s∈{0, 1, . . . , T−1} into {0, 1, . . ., M−1}, wherein x corresponds to a respective parameter of the secondarystations, s corresponds to a parameter of a subframe, X is a set of therespective x parameters of the secondary stations, T indicates a numberof hash functions, and M is constant, and wherein the hash function hasthe following properties: for each s∈{0, 1, . . . , T−1}, the functionf_(s), attains each element in {0, 1, . . . , M−1}, approximatelyequally often; and for all distinct s,t in {0, 1, . . . , T−1}, where tis a different subframe than s, the number of elements x in X is suchthat f_(s),(x)=i and f_(t)(x)=j are approximately the same for allvalues of i and j.
 22. The method of claim 16, wherein the hash functionhas the form:f(x,s)=(h(x)modg(s))modM, where x is an identifier of the secondarystation, h is a function dependent on x, s is an identifier of asubframe, g is a function dependent on s, M is a quantity of resourceelements, and mod is the modulo function.
 23. The primary station ofclaim 8, wherein the hash function fs(x) results in a substantiallyuniform probability of configuring each of the available resources to agiven secondary station in a given subframe.
 24. The primary station ofclaim 8, wherein for two distinct subframes s, t, the outputs of thehast functions fs(x), ft(x) are substantially independent from eachother.
 25. The primary station of claim 8, wherein the parameter of thesecondary station is an identifier of the secondary station, theidentifier being different for each different respective secondarystation of the network.
 26. The primary station of claim 8, wherein thehash function has the form:f(x,s)=(h(x)modg(s))modM, where h is a function dependent on x, g is afunction dependent on s, M is a constant, and mod is the modulofunction.
 27. The primary station of claim 26, wherein h(x) is aconstant multiplier.
 28. The primary station of claim 26, wherein foreach value of s, g(s) is a prime number.
 29. The primary station ofclaim 9, wherein the hash function fs(x) results in a substantiallyuniform probability of configuring each of the available resources to agiven secondary station in a given subframe.
 30. The primary station ofclaim 9, wherein for two distinct subframes s, t, the outputs of thehash functions fs(x), ft(x) are substantially independent from eachother.
 31. The primary station of claim 9, wherein the parameter of thesecondary station is an identifier of the secondary station, theidentifier being different for each different respective secondarystation of the network.
 32. The primary station of claim 10, wherein thehash function has the form:f(x,s)=(h(x)modg(s))modM, where h is a function dependent on x, g is afunction dependent on s, M is a constant, and mod is the modulofunction.
 33. The primary station of claim 32, wherein h(x) is aconstant multiplier.
 34. The primary station of claim 32, wherein foreach value of s, g(s) is a prime number.
 35. The primary station ofclaim 14, wherein the hash function fs(x) results in a substantiallyuniform probability of configuring each of the available resources to agiven secondary station in a given subframe.
 36. The primary station ofclaim 14, wherein for two distinct subframes s, t, the outputs of thehash functions fs(x), ft(x) are substantially independent from eachother.
 37. The primary station of claim 14, wherein the parameter of thesecondary station is an identifier of the secondary station, theidentifier being different for each different respective secondarystation of the network.
 38. The primary station of claim 14, wherein thehash function has the form:f(x,s)=(h(x)modg(s))modM, where h is a function dependent on x, g is afunction dependent on s, M is a constant, and mod is the modulofunction.
 39. The primary station of claim 38, wherein h(x) is aconstant multiplier.
 40. The primary station of claim 39, wherein foreach value of s, g(s) is a prime number.
 41. The primary station ofclaim 15, wherein the hash function fs(x) results in a substantiallyuniform probability of configuring each of the available resources to agiven secondary station in a given subframe.
 42. The primary station ofclaim 15, wherein for two distinct subframes s, t, the outputs of thehash functions fs(x), ft(x) are substantially independent from eachother.
 43. The primary station of claim 15, wherein the parameter of thesecondary station is an identifier of the secondary station, theidentifier being different for each different respective secondarystation of the network.
 44. The primary station of claim 15, wherein thehash function has the form:f(x,s)=(h(x)modg(s))modM, where h is a function dependent on x, g is afunction dependent on s, M is a constant, and mod is the modulofunction.
 45. The primary station of claim 44, wherein h(x) is aconstant multiplier.
 46. The primary station of claim 44, wherein foreach value of s, g(s) is a prime number.